4. Pilot

We're so used to air travel as an accessible convenience that we often forget how outrageous it is to be soaring through the air, enjoying complimentary beverages and peanuts, at deadly speeds and oxygen-free altitudes. Pilots don't forget this, because they're the ones who make sure we get from ground to air and back safely, and their job is difficult enough that there's always a constant threat of something going terribly wrong. Commercial pilots have a daunting fatality rate, and test pilots, their badass military counterparts, do similar work under even more stressful conditions.